Hearing aid users describe the occlusion effect and jaw motion induced feedback problems as major causes for hearing aid dissatisfaction. The proposed work would define groundwork for a thorough understanding of the human ear canal and the design of a safe and effective deeper insertion earpiece that has minimum contact with the dynamic cartilagenous region of the canal. With 6 carefully chosen subjects, deep silicone ear impressions and MRI methodologies will be evaluated for utility in visualizing important topography and sub-structure of the ear canal. Data obtained will allow subject-specific design of protypical earpieces. Measurements will be taken to determine effectiveness in reducing the occlusion effect and jaw motion induced feedback with in-the-ear hearing aids with experimental earpieces. In the U.S. more than 3 million existing hearing aid users and 60% of all new users could benefit from a successful deeper insertion earpiece. The Phase I technical team involves audiology, biophysics, otology and radiology talent, led by the principal investigator, an experienced inventor and builder of new hearing health business. The company, having already developed one earpiece to commercialization, is ideally positioned to bring a successful deeper insertion earpiece to the hearing marketplace through many hearing aid manufacturers.